<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>rem</title>
	<style>
		.div1{width: 10rem;height: 10rem;background: red;}
	</style>
</head>
<body>
	<div class="div1"></div>
	<script>        
        (function (doc, win) {    
            var docEl = doc.documentElement,    
            resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',    
            recalc = function () {    
            var clientWidth = docEl.clientWidth;    
            if (!clientWidth) return;    
            docEl.style.fontSize = 10 * (clientWidth / 1304) + 'px';    
        };    
        if (!doc.addEventListener) return;    
        win.addEventListener(resizeEvt, recalc, false);    
        doc.addEventListener('DOMContentLoaded', recalc, false);    
        })(document, window);    
    </script>
</body>
</html>